Process for making hydrochloric acid and recovering metal oxides



Oct. 16, 1956 N. c. CHRISTENSEN 2,767,056

PROCESS FOR MAKING HYDROCHLORIC ACID AND RECOVERING METAL OXIDES Filed April 13, 1953 2 Sheets-Sheet 1 LEACHER. 1

Nn ORE LEACH ER. or SULPHAT OR.

WASH

SOLUTION MIX-1504. S02 anvil- 50 SOLUTION or 5OZ+O ORE RESIDUE. WASH WATER a W FILTER. 1- J MnO E g: g 5 YCONCEZNTRATOR. I

2 3 "5"PRECIPI'IATOR. 3 g I! m #1 H25 0 FILTER or v CENTRIFUGE SULPHIDE. F LT o PRECIPITATE. 1 ER E Mnso n o CRYSTALS g Mn s0 SOLUTION Q g 7 DRYER g g 5 con CENTRA'IOR, HQ GASES Mnso} I m ALKALI CHLORIDE M V,

FILTER or DECOMPO sma 6 CEN'IRIFUGE M 50 1-120 4 8 STEAM 81, OXYGEN CRYSTALS '7 DRYER- 9 COOLER.

' N HCl GASES M11504.

ALKALI. CHLORIDE z 10 o A E E LEACHER. m 8 DECOMPOSER. g g o 2. m g STEAM 8L OXYGEN WASH WAT ER. 2 311x211 g 9 COOLER. DRYER 11 H I z 3 N a 2 5 O4: 8 z SOLUTION 0 5 I; LEACHER 3 10 RECOVERED WASH WATER. k

Mnzog? INVENTOR FILTER. 12 11 'Nlels C.Chr1scensen DRYER.

M32504 SOLUTION BY ATTORNEYS Oct. 16, 1956 N. c. CHRISTENSEN 2,767,056

PROCESS FOR MAKING HYDROCHLORIC ACID AND RECOVERING METAL OXIDES Filed April 13, 1953 2 Sheets-Sheet 2 ALKALI METAL. CHL ORIDE FERROUS SULPHATE. F8 2 O 3 5/ '51 MIER Fis. 3

C AS V H I G 32 DE COMPOSER,

STEAM (Sb OXYGEN In C) N 33 2 co OLER 9 E WASH g3 SOLUTION J D 5 U LEACHER 'WASH WATER.

35 FILTER.

ALKALI METAL SULPHATE. SOLUTION 56 DRYER.

LRE COVERED Fe 0 INVENTOR Niels C. Chriscensen ATTORNEYS Unitecl States Patent PROCESS FOR MAKING HYDROCHLORTC ACID I AND RECOVERING lVIETAL OXIDES Niels C. Christensen, Bauer, Utah Application April 13, 1953, Serial No. 348,480

Patented Oct. 16, 1956 ice 1 the flow sheets illustrated therein are similar, except that 17 Claims. (Cl. 23-15l4)' This application is a continuation-in-part of my appli-.

cation Serial No. 217,838, filed March 27, 1951, now abandoned.

The invention relates to processes for the hydrochloric acid from alkali metal chlorides, particularly potassium and sodium chlorides. The invention further relates to a combined process for the treatment of either manganese or iron sulphate to recover manganese oxide and ferric oxide, respectively, and to the manufacture of hydrochloric acid from alkali metal chlorides, especially sodium and potassium chlorides.

In the particular case of the invention where manganese sulphate is used, the invention comprehends the treatment of manganese ores or products to recover manganese therefrom as a sulphate for use in the treatment of the alkali metal chlorides to make hydrochloric acid therefrom. The essential steps of the process where manganese sulphate is used are such that it may be used either for the manufacture of hydrochloric acid alone, or for the treatment of manganese ores for the recovery of manganese therefrom as an oxide and the manufacture of hydrochloric acid. Since the cost of carrying out the process will be substantially the same in either of these cases, the preferred application of the process will be for the treatment of the ore and the making of the acid, though the process may be economically used where manganese ore suitable for treatment is not available.

Referring more particularly to the embodiment of the invention involving the use of manganese sulphate:

The process consists of two principal steps or parts first, the treatment of a mixture of finely divided manganese sulphate and alkali metal chloride with steam and oxygen at a suitable temperature high'enough to cause the decomposition of the manganese sulphate and alkali chloi ide and formation of hydrochloric acid, manganese oxide and sodium sulphate, as indicated in the following equation:

The accompanying drawings illustrate by means of flow sheets the more detailed description of the processes and the methods of carrying it out, the same as given below. In the drawing:

Figure 1 represents a flow sheet illustrating the combined process for the treatment of manganese ore and the making of hydrochloric acid;

Figure 2 is a flowsheet illustrating thep'rocess as making:

in Figure 2, the filter 2 and. precipitator 3 and filter 4 are omitted, as the MnSOr used in the process shown in Figure 2 is made from M11203 recovered in the process and used over and over again cyclically, and there is,-

therefore, no ore residue to be separated from the MnSOr solution or impurities to be precipitated from the MnS04 solution. Thesame numbers indicate the same or simih and 2. Y

recovered in the process is used over and over again,

Referring more particularly to the flow sheets of Figures 1 and 2, the first step in the process consists in treating the ore, or manganese oxide product for the recovery of the manganese in solution as manganese sulphate by leaching the ore, or Mn2Oa product, with S02, or S02 and 0, or S02 and H2804. If the manganese in the ore is substantially all in the form of MnO2, the leaching process is carried out with S02 alone, the manganese being recovered in solution as MnSO4,

as indicated in the following chemical equation:

If the ore contains lower oxides of manganese, such as Mn203, the MnSO4 may be made by treatment of the ore with H2504 and S02, as indicated below:

As shown in flow sheet of Figure 2, in cases where no suitable manganese ore is available, manganes oxide cyclically, to make the MnSOr required in'the process, by treatment of this M11203 with S02 and H2804 (or S02 and O) as indicated in the following chemical equations:

M11203+SO2+H2SO4= 2MnSO4+H2O Mn203+2S02+O=2MI1SO4 The leaching operation for the recovery of Mn from the ores as MIISO4 (flow sheet of Figure No, 1), or preparation of MnSO4 from Mn20a- (flow sheet of Figure No. 2),

or preparation ofthe MIISO4 in solution is preferably carried out by mixing the finely ground ore (or Mn203) with water (preferably wash solution from the filtering or decanting operation in which the MnSOa solution is separated from ore residue, in case the process is used for the treatment of ore) to form a slurry and treating the slurry with S02 gases in a spray leacher 1 of the type shown in U. S. Patent No. 2,454,594, but may be carried out in any apparatus suitable for bringing the mixture of ore and solution into intimate contact with the S02 gases. If H2504 is required in the leaching step and washing step may: be

' H25 in a suitable agitator 3 to secure a pure sulphide precip-itate as indicated in the following equations:

( M indicating any one or more of the metals otherthan manganese the solution). If a pure precipitate 1s not desired, these metals may be precipitated together with CaSQ ZHzO by means of CaCO3 and H23 in a suitable spnay agitator ,3, preferably of .the type described in U. S.

Patent No. 2,454,594 (or any other suitable apparatus),

or with Ca(SH)z as indicated in'the following equations:

' (If the process is being used for the manufacture of HCl alone, this cleanup or precipitation step and the succeeding filtering operation are, of course omitted-as indi cated in flow sheet of Figure No, 2.) The MS PI'BClPi'; tate is separated from the MnSOr solution by filtering and washing on the filter 4. V

The pure MnSOrso'lution made in these leaching operations is concentrated by heating and evaporation to recover the manganese therefrom as MnSO4.I-I2O in a suitable concentrator 5, This operation is preferably carried out in two-steps, a sprayevaporation in which the solu tion is heated by condensation of steam from the suc- 'ceeding step and the solution evaporated by passage of air through the heated solution in a suitable spray apparatus of the type described in U. '8. Patent No, 2,454,593 (or any suitable device), followed by a final evaporation step in which MnSO4.H2O is precipitated to form a relatively'thick slurry of these crystals in a concentrated residual lVInSO4 solution. This operation is preferably conducted in apparatus in which the heat from the hot M11203 product from the decomposing operation is cooled and its heatused in this final concentrating and crystallizing'operation. a

T e MnS t-H2O rystal fr m th rystallizing op ion are separate from the r si ual MnS04 s lu i n in a centrifuge or filter 6 and the concentrated residual MnSOr solution is returned to the concentrating and crystallizing operation (as indicated on the flow sheets). The MnSO4.H2O crystals are of such character that they re eas ly sep ra ed from C1 bo residual solution re in ring rel ti ly e y sm qu pm n ther centri uge r fi n- The M SOaHa ys als m he cen rifug or filter ,6 are dried in a. suitable dryer 7. This operas-l n ot ers no diffic y s n Without melting or fritting. V

The ry M1804 is fin y g un a d thoroughly mixed the cry tals dry eadily with finely d vided dry NaCl (or KCl) and with, MnzOs in s tfici nt quanti y to pr en fusi g r trifling of the mixture during the decomposing operation. If the mixure of M1150; and lk li chloride i rea ed al ncx without mixture and dilution with inert solid, material in the decomposing operation, it will melt or frit at any temperature at which the, decomposition is .sufficiently rapid to be economically feasible (due to the long time of treatment required for'complete decomposition at lower temperatures). The charge to the decomposer 8 is t'herein approximately the following proper.

fore made up tions:

"10 parts M11504 8 parts NaCl (01 105 parts KCl) 75 p r s (o m re) M 203 In these proportions, the sodium chloride is about 5% 4 in excess of that required according to the equations given below, but a slight excess of chloride is necessary to secure complete decomposition of the MnSO4. This mixture is heated, preferably in countercurrent, with steam and oxygen (air or pure oxygen) to a temperature of approximately 700 C., at which temperature the MnSO4 and alkali chloride and steam and oxygen react to form M1120 Na2SO4 and ,HCl, indicated in the following equation:

coming more pronounced as the temperature decreases, and the required excess of steam and oxygen also-increase with decrease in temperature. The decomposing opera tion may be carried out in any suitable kiln or furnace 8,'

either by direct or indirect heating and either with air or pure oxygen, depending upon the concentration of HCl desired in the gases from the decomposer. If the mostconcentrated gas is required, the operation may be carried out'in a muflle type furnace using oxygenand steam in contactwith the solids in the charge. If a less concentrated HCl' gas is satisfactory, air may be 'used instead of oxygen alone. The decomposition may also be carried out in a rotary kiln by passing the charge through the kiln in countercurrent with. the hot steam and oxygen or air. If a very concentrated HCl gas is required, the heating maybe done by burning hydrogen and oxygen to form steam and using thehot steam and an excess of oxygen to heat t'he, charge and to decompose the salts as described above and as indicated in the following equations: a

A somewhat less concentrated HCl gas may be secured V by the'same method by using natural gas and oxygen, 7 the HCl gas in this case being diluted with CO z as indie,

ated in thefollowing equations:

CH4+2O2=2H2+CO2 2MuSQ4+4NaCl+ZH O+O=MnzO3+2NazSQt+4HC1 If only a very dilute *HCl gas is required, the heating in the kiln may be done by means of oil or coal dust and air, the required amount of steam being supplied froma boiler r o her source. To secure rapid and completeec mposifi not the alkali chloride and M11804 as indi'c tcd in the foregoing equations, itis necessary to :use an excess of steam and oxygen, but, by conducting the operation so that the gases and solids move .co untercur rently during the. heating and decomposing operation, the

excess steam and oxygen orair may be kept at a mini mum.

The hot mixture of Na2SO4 and M11203 (consisting of the M11203 formed from the MnSO; together with the circulating Mn2O3) from the decomposer 8 is cooled in a cooler 9 (preferably, as noted above, in such a manner as to utilize the heat in this mixture in the concentratlng and crystallizing operation) and the mixture is leached with water in the leaching agitator 10 to dissolve the NazSOt and form a Na2SO4 solution which is separated from the M11203 filter or centrifuge 11.

Below 700 C., the rapidity of the reaction 7 by filtering and washing on the' enemas he..MnSO4 and NaOl (or KCl) and sent to the. decom' poser-'8 for re-use in the process as described; the amount of M11203 recovered from ore, asv indicated. in flow sheet of Figure No. 1, being separated from the circulating M11203 before the latter is returned to. the mixing and decomposing operation. In case no ore is treated, as in flow sheet of Figure No. 2, sutficient of the M11203 is converted to M11504 in each cycle as described above for use. in the decomposition of the alkali metal chloride, as described above and as indicated in flow sheet of Figure No. 2.

As will be seen from the foregoing, the inventionmakes possible the manufacture of hydrochloric acid from alkali metal chlorides by a simple and efficient process in which a pure acid is made and high grade sodium sulphate is recovered. Used for thispurpose alone, the process is both elficient and economical and requires a much less elaborate and expensive plant than past methods for making hydrochloric acid from S02 and NaCl (or KCl). When used for the combined treatment of manganese ores and the manufacture of hydrochloric acid and alkali sulphate, as described above, the invention offers a process so much more efficient and economical (than when used for the manufacture of HCl alone) that all the advantages a-re greatly increased since, for substantially the same cost, it is possible to both treat the ore for the recovery of the manganese and make an equivalent amount of HCl and NazSOc.

As stated above, a quantity of MnaOs is added and thoroughly mixed with the finely divided M11504 and dry NaCl (or KCl), introduced into the decomposer, for the purpose of preventing fusing or fritting of the mixture during the decomposing operation. MnaOs, there can be used for this purpose any other suitable inert material, such as quartz, sand, =etc., which does not take part chemically in the decomposingprocess. If .a mixture of MnSO4 and NaCl alone were treated in the decomposer, they would form a molten mass in thedecomposing furnace at any decomposition temperature sufficiently high to render the process economically practicable. Due to the formation of a molten mass, the decomposition reaction becomes so slow as .to be impractical, since the amount of surface exposed to the steam and oxygen is so small and is quickly covered with a thin layer of M11203 which prevents further action. For this reason, a relatively finely divided solid inert diluent is. necessary to distribute the mixture of alkali metal chloride and MnSOx over a large surface for contact with the steam and oxygen. Any inert diluent, such as silica, sand or MnzOs may be used, but the ,MnzOs is preferred since, when it is used, there is no need of separating the M1120: produced in the process from the diluent.

As has been stated above, the action in the decomposer may be represented by the following equation:

An excess of steam and oxygen of 25% or more than indicated in the above equation is required for complete decomposition as indicated in the equation. 'By carrying out the decomposing process in countercurrent, i. e. passing the steam and oxygen and the mixed solids through the heating furnace in opposite directions, a complete reaction as indicated may be secured, and the highest possible concentration of HCl in the exit gases is also obtained.

It should also be observed that if the ,MnSOs and NaCl are very finely ground and thoroughly mixed before being heated and treated with the steam and oxygen, the temperature used in the decomposing process may be as high as 850 C. without appreciable loss of $03. A temperature of 700 (3., however, is high enough to secure a rapid reaction with a relatively small excess of steam and oxygen; a temperature of 700 C. or slightly higher is, therefore, preferred.

vAs disclosed earlier in the specification, the present in- In lieu ofv vention, also comprehends a process for makingahvdrm chloric .acid from, alkali metal chlorides, particularly; sodium and potassium chlorides, and for the. recovery of the iron from ferro ulphate s .fern'c oxide, the alkali metal being recovered in the process as a sulphate. This embodiment of the invention is more particularly .lH'l-lSe trated. in the flow sheet of Figure 3, This/variantof the invention may be utilized for the manufacture .of by drochloric acid, using ferrous sulphate from any source, but is particularly useful in connection with the; treatment of ferrous sulphate recovered from ilmenitethe manufacture of titanium oxide, and from other processes in which ferrous sulphate is. recovered as a byproduct oras a waste product.

In; general, this modification of the process of themvention consists of the treatment of a. mixture of finely divided metal, chloride and finely divided ferrous sulphate with steam and oxygen at a high enough temperature to cause the decomposition of the alkali. chloride and the ferrous sulphate with the formation of hydrochloric acid, ferric oxide and alkali metal sulphate, as indicated in-the following equation:

' eration of the decomposition process. v Sufficient circu-- lating ferric oxide must be used to prevent fusion oft-he} mixture inthe decomposing step; should the mixtu-re'ofchloride and ferric oxide form afluid or sticky mass during the heating operation, then, the decomposition is so slow as to be economicallyimpractical. If -a mixture" of alkali chloride and ferrous sulphate alone be treated with the steam and oxygen (oxygen alone or air); at a high enough temperature to cause decomposition, the

mixture fuses and the decomposition is so retarded that it becomes impractical; also, the decomposition cannot be carried out'by reason of the adherence or sticking of'the mass to the walls of the decomposer. For this reason, and as disclosed earlier in this specification, sufficient finely divided ferric oxide, or other suitable inert soiid finely divided diluent, must be used to prevent the fus-.

ing or frittin g together or agglomeration of the mixturei. e. a large enough surface of'ferric oxide or other inert diluent particles must be provided to distribute the mixture of alkali metal chloride and ferrous sulphate andthereby expose a very large surface of the mixture of alkali chloride and ferrous sulphate to the-action ofthe steam and oxygen.

To insure this intimate mixture of the charge, thealkali chloride and ferrous sulphate may be mixed first and, thereafter, this mixture is mixed with the circulat ing ferric oxide. .In order to secure a complete decomposition of the ferrous sulphate, a small excess of the alkali metal chloride may be usedif it be desired to imsure that no undecomposed iron salts remain in the treated product to contaminate the alkali metal sulphate produced in the process. A mixture in approximately the following proportions has been found very satisfactory inthedecomposing step:

10 parts ferrous sulphate 8 parts sodium chloride, and 76 parts ferric oxide W th K01, a sl ghtly larger pr portion of ferric oxide gives-the best results.

The mixture of alkali metal chloride, ferrous sulphate;

and fe rric oxide, in approximately the proportions, indicated above, is treated with steam and oxygen in the :de-

, composer 32 at a temperature high enough to secure rapid and complete decomposition. An excess of both steam and oxygen is required for complete decompositionL At 500 C., the reaction is. rapid and complete in.

in the neighborhood of 550-600 C., gives a sufliciently rapid decomposition for all practical purposes. Potassium chloride gives'better results 'at a slightly higher temperature than that required for sodium chloride;

In the decomposition step, steam and either 'pure oxygen, air enriched with oxygen,- or ordinary air, may be. used-depending upon the concentration of HCl required or desired in the gases resulting from'thedecomposition reaction. -In the annexed claims, the term oxygen. is used to denote any gas containing free oxygen, such as oxygen alone, air enriched with oxygen or ordinary air. The decomposition is somewhat more rapid with gases having higher concentrations of oxygen, and the size of apparatus required is, of course, diminished with increase in the concentration of oxygen due to the smaller volume of gases required.

j The decomposition may be-carried out in a rotary or any other type of apparatus in which the required temperature may be maintained and an efiicient contact between the gases and solids maybe secured.

-, The hot mixture of ferric oxide and alkali-metal sulphate fromthe decomposer32jis cooled in any suitable cooler 33 and is then leached with a water solution in the leacher 34, the alkali sulphate being thus brought into solution and is, thereupon, separated from the ferric oxide by filtration and washing on the filter 35; the wash solution from this operation is used for the dissolving operation, as indicated in the flow sheet of Figure 3.

1 The. washed filter cake of ferric oxide is dried in any suitable form of drier 36, and an amount of ferricoxide corresponding to that produced from the ferrous sulphate is. separated from the dried product and removed from the system; the remainder of the ferric oxide is used over again inadmixture with more alkali metal chloride and ferrous sulphate in the decomposition process, as above described. 7 7 The recovery of FeSO4-for use in the process de-' scribed above-from a sulphuric acid solution, .though somewhat more difiicult than its recovery from -a water solution, presents no serious ditficulties if carried out as follows:

The acid solution is heatedand evaporated until there is formed a slurry of crystals of FeSO4.H2O in a solution of approximately 60% H2504. This acid solution carries little more than atrace of ir0n,'as FeSO4. The crystals ofFeSOaHzO are separated from the concentrated H2804 solution by filtration or by means of a centrifuge. The filter cake is heated to drive off the residual H2504 and water and the dried FeSO4 product is pulverized to prepare it for the decomposition process described above. ,The concentrated H2804 solution, as noted above, contains a very small amount of iron and 7 may generally beutilized in the process from which it cient to compensate for the diificulties encountered when working at temperatures higher than those indicated.

' :i By the process above described, a relatively very pure HCl may be made from alkali metal chlorides and a highgrad FezOa product may be recovered from the FeSO4, further,'the alkali metals and SO; may be recovered as arelatively pure alkali 'metal sulphate." f V Having described my invention, .what I claim an desire to patent is a I -1. a The process of making hydrochloric acid which con; sists in heat-inga mixture comprising a sulphate from the group consisting of ferrous sulphate and'manganous sulphate and an alkali metal chloride in the proportion of substantially two molecules of alkali chloride to one molecule of metal sulphate, and an oxide of the metal of the sulphate used, said oxide being selected from the group consisting of ferric oxide and manganic oxide in the amount of more than four times the combined weight of the said sulphate and chloride,'said heating being to a temperature between 500 and 600 C. in the case of the ferrous sulphate, and said heating being to a temperature between 700 and 850 C. in the case of'manganous sul: phate, and said heating being efiected in contact with a current-of gas containing a mixture of steam and oxygen in the proportion of substantially one molecule of elemental oxygen to four molecules of steam, and thereby de composing the alkali chloride and the metal sulphate and forming hydrochloric acid gas and alkali metal sulphate and metal oxide, and removing the hydrochloric acid gas from the mixture of alkali metal sulphate and metal oxide; 2. A process according to claim '1, wherein the contact between said solids and gases is carried out with counter current fiow'of said solidsand gases. 7 V

3. A process according to claim 1, wherein the metallic' sulphate is ferrous sulphate and the oxide is ferric.

oxide.

4.'A process according to claim 3, wherein the contact between said solids and said gases is carried out with countercurrent flow of said solids and gases at a temperature within the range of 550-600 C.

5.A process according to claim '3, wherein said alkali metal sulphate is separated from said ferric oxide'by leaching with water, filtering and washing of the ferric oxide.

6. A process according to claim 3, wherein the alkali metal sulphate is separated from the ferric oxide by.

leaching with Water, filtering and washing of theferric oxide, and wherein a portion of the washed ferric oxide, substantially equal in amount to that formed from the ferrous sulphate, is removed from the system, while the remainder of the washed ferric oxide is added to a.

'moved from the system, while the remainder of the dried V ferric oxide is added to a further mixture of alkali metal chloride and ferrous sulphate tobe decomposed. V p

. 8. The process of claim '1, wherein the metallic sulphate is manganous sulphate and the oxide is manganic oxide.

9. A process according to claim 8, wherein a portion of the manganic oxide is separated from the alkali metal sulphate, is' converted into manganous sulphate by treating.

it in the condition of an aqueous pulp with S0 2 and H2804,

and the resultant manganous sulphate is used in the decomposition of more alkali metal chloride as described. a 10. A process according to claim 8, wherein a portion of the mangani-c oxide is separated from the alkali metal' sulphate, is converted into manganous sulphate by treating it with $02 and oxygen, and the resultant manganous sulphate is used in the decomposition of more alkali metal chloride as described. 7

11. A processaccording to claim 8, characterized in that a portion of the manganic oxide is separated frorn' the alkali metal sulphate, and is'converted to manganous sulphate, and the latter is used in the decomposition of more alkali metal chloride as described.

12. A process according to claim 8, wherein the treatment is carried out at a temperature of about 700 C.

13. A process according to claim 8, wherein the contact between said solids and gases is carried out with countercurrent flow of said solids and gases.

14. A process according to claim 8, wherein the contact between said solids and gases is carried out with countercurrent flow of said solids and gases, and said heating takes place at a temperature c-E approximately 700 C.

15. The combined process of treating oxide ores of manganese and maln'ng hydrochloric acid, which comprises the steps of: leaching said ores with sulfur containing reagents which convert the contained manganese into manganous sulphate in solution; separating the manganous sulphate solution from the ore residue; heating and concentrating said solution so as to recover the manganous sulphate therefrom as a solid; drying and grinding said solid product and mixing the resultant finely divided manganous sulphate with finely divided alkali metal chloride, and manganic oxide in the amount of more than four times the combined weight of the said sulphate and chloride; heating said mixture to a temperature between 700" and 850 C. in contact with a current of hot steam and oxygen and thereby decomposing said alkali 'metal chloride and manganous sulphate and forming hydrochloric acid gas, alkali metal sulphate and manganic oxide; separating the hot hydrochloric acid gas from the hot mixture of manganic oxide and alkali metal sulphate; cooling said last mixture and leaching it with water to recover the manganic oxide and alkali metal sulphate as separate products.

16. A process according to claim 15, wherein the manganic oxide recovered from the leached mixture is segregated into two parts and one part is added to the mixture to be decomposed.

17. A process according to claim 15, wherein the leaching of the manganese ores is carried out with S02 and oxygen.

References Cited in the file of this patent UNITED STATES PATENTS 2,002,859 Levy May 28, 1935 FOREIGN PATENTS 359 Great Britain Feb. 5, 1872 OTHER REFERENCES A Comprehensive Treatise on Inorganic and The- 25 oretical Chemistry, vol. 12, page 416, 1932 ed. and Vol.

14, 1935 ed., pages 264, 278, author, I. W. Mellor; Longmans, Green and Co., N. Y. 

1. THE PROCESS OF MAKING HYDROCHLORIC ACID WHICH CONSISTS IN HEATING A MIXTURE COMPRISING A SULPHATE FROM THE GROUP CONSISTING OF FERROUS SULPHATE AND MANGANOUS SULPHATE AND AN ALKALI METAL CHLORIDE IN THE PROPORTION OF SUBSTANTIALLY TWO MOLECULES OF ALKALI CHLORIDE TO ONE MOLECULE OF METAL SULPHATE, AND AN OXIDE OF THE METAL OF THE SULPHATE USED, SAID OXIDE BEING SELECTED FROM THE GROUP CONSISTING OF FERRIC OXIDE AND MANGANIC OXIDE IN THE AMOUNT OF MORE THAN FOUR TIMES THE COMBINED WEIGHT OF THE SAID SULPHATE AND CHLORIDE, SAID HEATING BEING TO A TEMPERATURE BETWEEN 500* AND 600* C. IN THE CASE OF THE FERROUS SULPHATE, AND SAID HEATING BEING TO A TEMPERATURE BETWEEN 700* AND 850* C. IN THE CASE OF MANGANOUS SULPHATE, AND SAID HEATING BEING EFFECTED IN CONTACT WITH A CURRENT OF GAS CONTAINING A MIXTURE OF STEAM AND OXYGEN IN THE PROPORTION OF SUBSTANTIALLY ONE MOLECULE OF ELEMENTAL OXYGEN TO FOUR MOLECULES OF STEAM, AND THEREBY DECOMPOSING THE ALKALI CHLORIDE AND THE METAL SULPHATE AND FORMING HYDROCHLORIC ACID GAS AND ALKALI METAL SULPHATE AND METAL OXIDE, AND REMOVING THE HYDROCHLORIC ACID GAS FROM THE MIXTURE OF ALKALI METAL SULPHATE AND METAL OXIDE. 